Circular Electron Positron Collider

The Circular Electron Positron Collider (CEPC) is a proposed Chinese electron positron collider for experimenting on the Higgs boson. It would be the world's largest particle accelerator with a circumference of 100 kilometres (62 mi).^[1]

CEPC was proposed by the Chinese Academy of Sciences' Institute of High Energy Physics in 2012.^[2][1] Projections in 2023 were for a proposal to be submitted to the government in 2025, and construction taking place from 2027 to 2035; the projected cost was CN¥36.4 billion, including experiments.^[3]

The design was produced by a team of international physicists.^[1] The technical design report was released in December 2023.^[3]

CEPC is projected to have a maximum center-of-mass energy of 240 GeV.^[2] It will be located 100 metres (330 ft) underground, and have two detectors.^[1] The electron-positron collisions will allow clearer observations than the proton-proton collisions of the Large Hadron Collider (LHC).^[1]

After 2040, the collider could be upgraded into the Super Proton–Proton Collider^[2] with collision energies seven times greater than the LHC.^[1]

The CEPC enables a wide physics program. As an electron-positron collider, it is suited to precision measurements, but also has strong discovery potential for new physics. Some possible physics goals include:

• Higgs measurements: Running slightly above the production threshold for ZH, the CEPC is a Higgs factory. Over the course of a ten-year run, it is planned to collect 5 ab⁻¹ with two detectors, which corresponds to approximately one million produced Higgs Bosons.^[4] One target is to be able to measure the ZH production cross-section ${\displaystyle \sigma (ZH)}$ to 0.5% accuracy. Other goals include the measurement of the Higgs Boson self coupling, and its coupling to other particles.
• When running at the Z peak, a precision measurement of the Z Boson mass and other properties, e.g. the Zbb̅ coupling, can be made.^[5]
• Physics beyond the Standard Model:^[6] Despite the lower center-of-mass energy compared to the LHC, the CEPC will be able to make discoveries or exclusions in certain scenarios where the LHC cannot. A prominent situation is when there is supersymmetry, but the masses of the superpartners are very close to each other (near-degenerate). In this case, when one SUSY particle decays into another plus a Standard Model particle, the SM particle will likely escape detection in a Hadron collider. In an e+e− collider, since the initial state is completely known, it is possible to detect such events by their missing energy (the energy carried away by SUSY particles and neutrinos).

• Large Electron–Positron Collider – LEP was the highest energy lepton collider ever built
• Compact Linear Collider – another post-LHC linear particle accelerator planned at CERN
• International Linear Collider – another post-LHC linear particle accelerator planned in Japan
• Future Circular Collider – a proposed 100 TeV circular collider at CERN

• Record for CEPC on INSPIRE-HEP